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Takayuki Sasaki

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Conference paper (2026) - Ryu Kuki, Takayuki Sasaki, Arwa Al Alsadi, Carlos Gañán, Katsunari Yoshioka
In recent years, while the threat of cyber attacks and malware targeting the vulnerabilities of the Internet of Things (IoT) has become more serious, various efforts have been made to mitigate the spread of these threats and the damage they cause. This study aims to understand the mechanisms behind the increase and decrease in HTTP-based exploits targeting IoT devices, and to verify the effectiveness of current prevention and mitigation measures. By integrating attack analysis observed in honeypots, collecting malware samples, and publicly available vulnerability information, we visualize the temporal changes in the number of attacks over the lifetime of vulnerabilities, and identify the impact of life events such as the release of the proof-of-concept (PoC) or the weaponization into malware on changes in attack trends. Comparing attack volumes for vulnerabilities discovered from 2008 to 2024, we discover differences in attack trends depending on the age of the device and vulnerability. Our results show that attacks targeting new devices with adequate security measures tend to decrease relatively quickly, while attacks targeting older devices with inadequate measures often persist until the end of the device's life, by being weaponized in malware. These findings confirm that existing security measures are effective to a limited extent, but at the same time, they also show that continuous improvement and proactive measures are necessary to prevent the exploitation of vulnerabilities from continuing for long periods of time. ...

Piecing Together Factors of IoT Vulnerability Exploitation

Conference paper (2025) - Arwa Abdulkarim Al Alsadi, Mathew Vermeer, Takayuki Sasaki, Katsunari Yoshioka, Michel Van Eeten, Carlos Gañán
The proliferation of Internet of Things (IoT) devices has led to a surge in vulnerabilities, with traditional metrics like CVSS and PoC exploits failing to fully explain exploitation patterns. To address this, we leverage features from the-state-of-the-art prediction model EPSS – such as CVSS, CWE, vendors, external references, vulnerability age, and PoCs – and combine it with new features derived from hacking communities. Our study of 23,373 IoT-related CVEs and 25k posts from 25 hacking forums highlights the importance of including insights on attacker behavior from discussions involving vulnerabilities. We identified 38 features with a p-value < 0.05 that impact attackers’ selection of IoT vulnerabilities. We use two metrics to evaluate our model with features from hacking forums: McFadden’s pseudo R2, which showed a 21% improvement in explaining variance, and the Brier score for prediction accuracy, with a 17% improvement over EPSS. These results emphasize that current state-of-the-art methods struggle to capture the distinct nuances and complexity of IoT threats, and incorporating available information such as insights into attacker behavior can enhance the factors influencing the targeting of IoT vulnerability better. ...
Conference paper (2022) - Takayuki Sasaki, Akira Fujita, C. Hernandez Ganan, M.J.G. van Eeten, Katsunari Yoshioka, Tsutomu Matsumoto
Geographically distributed infrastructures, such as buildings, dams, and solar power plants, are commonly maintained via Internet-connected remote management devices. Previous studies on detecting and securing industrial control systems (ICS) have overlooked these remote management devices, as they do not expose ICS-specific services like Modbus and BACnet and thus do not show up in Internet-wide scans for such services. In this paper, we implement and validate a discovery method for these devices via their Web User Interface (WebUI) and detect 890 devices in Japan alone. We also show that many of these devices are highly insecure. Many allow access to the status or even the control over industrial systems without proper authentication. Taking a closer look at three prevalent remote management devices, we discovered 13 0-day vulnerabilities, several of which were rated as medium or high severity. They have been responsibly disclosed to the manufacturers. By using honeypots that imitate these systems, we show that over time, only a small number of attackers enter these systems, but some do change critical parameters. Attackers appear to interact more with the system when more facility information is displayed on the WebUI. Finally, we notified operators of 317 vulnerable remote management devices by email and telephone. We reached 212 persons in charge of the devices and received confirmation that our method had correctly identified the device. 50% of the persons in charge of the devices stated that they mitigated or will mitigate the problem. We confirmed their actions via a followup scan for vulnerable devices and found that measures were taken for 58% of the devices when we could reach the persons in charge of the device. ...

DDoS mitigation technique to deter financially-motivated attackers

Journal article (2020) - Takayuki Sasaki, Carlos Hernandez Gañán, Katsunari Yoshioka, Michel Van Eeten, Tsutomu Matsumoto
Distributed Denial of Service attacks against the application layer (L7 DDoS) are among the most difficult attacks to defend against because they mimic normal user behavior. Some mitigation techniques against L7 DDoS, e.g., IP blacklisting and load balancing using a content delivery network, have been proposed; unfortunately, these are symptomatic treatments rather than fundamental solutions. In this paper, we propose a novel technique to disincentivize attackers from launching a DDoS attack by increasing attack costs. Assuming financially motivated attackers seeking to gain profit via DDoS attacks, their primary goal is to maximize revenue. On the basis of this assumption, we also propose a mitigation solution that requires mining cryptocurrencies to access servers. To perform a DDoS attack, attackers must mine cryptocurrency as a proof-of-work (PoW), and the victims then obtain a solution to the PoW. Thus, relative to attackers, the attack cost increases, and, in terms of victims, the economic damage is compensated by the value of the mined coins. On the basis of this model, we evaluate attacker strategies in a game theory manner and demonstrate that the proposed solution provides only negative economic benefits to attackers. Moreover, we implement a prototype to evaluate performance, and we show that this prototype demonstrates practical performance. ...